title: High genetic diversity and distinctiveness of rear-edge climate relicts maintained by ancient tetraploidisation for Alnus glutinosa.
abstract: Populations located at the rear-edge of a species' distribution may have disproportionate ecological and evolutionary importance for biodiversity conservation in a changing global environment. Yet genetic studies of such populations remain rare. This study investigates the evolutionary history of North-African low latitude marginal populations of Alnus glutinosa Gaertn., a European tree species that plays a significant ecological role as a keystone of riparian ecosystems. We genotyped 551 adults from 19 populations located across North Africa at 12 microsatellite loci and applied a coalescent-based simulation approach to reconstruct the demographic and evolutionary history of these populations. Surprisingly, Moroccan trees were tetraploids demonstrating a strong distinctiveness of these populations within a species otherwise known as diploid. Best-fitting models of demographic reconstruction revealed the relict nature of Moroccan populations that were found to have withstood past climate change events and to be much older than Algerian and Tunisian populations. This study highlights the complex demographic history that can be encountered in rear-edge distribution margins that here consist of both old stable climate relict and more recent populations, distinctively diverse genetically both quantitatively and qualitatively. We emphasize the high evolutionary and conservation value of marginal rear-edge populations of a keystone riparian species in the context of on-going climate change in the Mediterranean region.
authors.affiliation: Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, United Kingdom ; INRA, UMR 1224, Ecologie Comportementale et Biologie des Populations de Poissons, Saint Pée sur Nivelle, France ; Univ Pau & Pays Adour, UMR 1224, Ecologie Comportementale et Biologie des Populations de Poissons, Anglet, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Lepais
authors.forename: Serge D
authors.initials: SD
authors.lastname: Muller
authors.forename: Samia
authors.initials: S
authors.lastname: Ben Saad-Limam
authors.forename: Mohamed
authors.initials: M
authors.lastname: Benslama
authors.forename: Laila
authors.initials: L
authors.lastname: Rhazi
authors.forename: Djamila
authors.initials: D
authors.lastname: Belouahem-Abed
authors.forename: Amina
authors.initials: A
authors.lastname: Daoud-Bouattour
authors.forename: Amor Mokhtar
authors.initials: AM
authors.lastname: Gammar
authors.forename: Zeineb
authors.initials: Z
authors.lastname: Ghrabi-Gammar
authors.forename: Cécile Fanny Emilie
authors.initials: CF
authors.lastname: Bacles
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000352:Africa, Northern; D029661:Alnus / Q000235:genetics*; D002980:Climate; D003198:Computer Simulation; D003247:Conservation of Natural Resources; D005060:Europe; D019143:Evolution, Molecular; D014644:Genetic Variation; D005838:Genotype; D005843:Geography; D018895:Microsatellite Repeats / Q000235:genetics; D008957:Models, Genetic; D057891:Tetraploidy